Method and apparatus positioning a read head to follow a track in a hard disk drive

TECHNICAL FIELD

0001The invention relates to positioning a read head to follow a track on a rotating disk surface within a hard disk drive, during the reading of the track.

BACKGROUND OF THE INVENTION

0002The invention relates to an improved use of servo track information to follow a track during a read operation. The track is situated on a rotating disk surface in a hard disk drive. Hard disk drives include at least one rotating disk surface accessed by a read-write head mechanically coupled to an actuator arm in a voice coil motor. The invention involves improving the control of at least the voice coil motor, and possibly a micro-actuator. The micro-actuator may be used to provide refinement of the positioning of the read-write head.

0003The voice coil motor is controlled through electrical stimulation of its voice coil, which interacts with the fixed magnet to pivot at least one actuator arm through the actuator pivot. As the actuator arm pivots, the read-write head is positioned over a data track on the rotating disk surface.

0004Tracks on a rotating disk surface include both a data track and a servo track. Servo tracks provide positioning information written onto the rotating disk surface. Typical servo track information includes a gray code representation of the track, as well as positional correction information. While in the past a separate rotating disk surface was sometimes reserved for the servo track information, today it is common for the servo track information to be multiplexed with the data on each rotating disk surface to be accessed. The data track is where the data for the application system is stored by the hard disk drive.

0005Different methods are used to position the read-write head for reading and for writing the data track. When reading the data track, the read head is positioned to follow the servo track of the data track. When writing the data track, the read head is positioned near a different servo track located some distance from the data track. This distance is the distance between the read head and the write head, which today is often over twenty tracks apart.

0006The process of writing the servo tracks onto a rotating disk surface is known as servo writing. Servo writing may be done inside an assembled hard disk drive. Alternatively, servo writing may be performed before the disks are assembled in the hard disk drive. Given the reliability of the disks today, there are economic advantages to assembling the hard disk drive before servo writing.

0007Each track on a rotating disk surface typically conforms to an overall structure. For example, a track often includes multiple sectors. Each sector typically includes a collection of at least two, often four and sometimes six Position Error Signal (PES) bursts. While it is possible for an odd number of PES burst signals to be useful, the discussion herein will focus on even numbers of PES burst signals. These PES bursts are written as part of the servo write process. The servo write process is used to operationally define the tracks on the rotating disk surface. The tracks, once operationally defined, persist when the power is turned off to the hard disk drive. The PES bursts allow the servo controller of the hard disk drive to sense the position of the read head over a track to a fraction of the track width. The fraction of the track width may be one half or less of the track width.

0008Mechanical vibrations are often experienced during the servo writing of tracks. These vibrations may result from external and/or internal vibrations. Mechanical vibration during the servo writing of tracks may result in the PES bursts for a track following a trajectory not exactly matching the track center. The consequence of this trajectory discrepancy is that the PES burst information may mislead a servo-controller, potentially degrading the ability of the hard disk drive system as a whole to position a read head to follow the track.

0009To minimize the possibility of PES burst trajectory discrepancies misleading the servo controller, several attempts to correct this problem are found in the prior art. Most of these attempts are algorithms designed to correct the trajectory discrepancies found in the PES bursts for a track. Most are based upon some form of iterative learning process. These iterative learning processes tend to collect PES values derived from calculations based upon sampling the track for multiple disk rotations. These collected PES values and/or results of the calculations are usually written to the disk for the tracks showing trajectory discrepancies.

0010These prior art corrective measures tend to add to the production cost by adding to the time required to initialize the rotating disk surfaces within assembled hard disk drives. In order to minimize production cost, data tracks are scanned to determine the quality of their PES bursts in matching the track trajectory. The prior art PES corrective algorithms are only applied to those tracks with the worst PES bursts. Data tracks with very bad PES quality for write mode are often rejected, rather than incur added production costs.

0011It is common in the prior art for the metric defining PES quality to differ between read mode and write mode. The PES quality for write mode is commonly seen as more important than the PES quality for read mode. Consequently, the acceptable PES quality for read mode tends to be lower than for write mode.

0012These conditions in the prior art lead to the following situation. When a hard disk drive has one or more read errors for a track due to poor PES quality for write mode, there is a common approach taken to correct this situation. The approach adjusts the positioning offset around the track for the read head. The read head then attempts to access the track. Depending on the PES quality for write mode, it may take several offset attempts, each for at least one disk rotation, to successfully access the track. This approach is known as an off-track then read retry sequence.

0013The off-track then read retry sequence is time consuming, and often adds to production expenses during quality testing of assembled hard disk drives. Consequently, it is a common production practice to turn off the off-track then read retry sequence during the initialization of rotating disk surfaces within assembled hard disk drives. This can lead to tracks with poor PES quality for write mode causing their hard disk drives to fail production testing.

0014What is needed is a quick way to offset the read head position around a track with a high probability of success, when the track has failed to be read. This need extends both to the initialization of a hard disk drive after assembly, as well as to the hard disk drive in normal operation.

BRIEF SUMMARY OF THE INVENTION

0015The invention includes a read positioning method and apparatus supporting the positioning method in a hard disk drive. The method positions at least one read head accessing a track on at least one rotating disk surface in a hard disk drive. It provides a quick and efficient way to adjust the read position of the read head based upon the Burst Correction Value of the nearest write track, when the PES burst patterns of the read track and nearest write track match.

0016The apparatus supporting the read positioning method may include a means for at least partly performing each step of the read positioning method. The means may include the following. Means for determining the read PES burst pattern of the read track. Means for using the read track position of the read track to find a nearest write track position for a write track. Means for predicting the write PES burst pattern of the write track. And means for adjusting the read position of the read head by the Burst Correction Value of the write track whenever the write PES burst pattern matches the read PES burst pattern. At least one of the means may include at least one instance of at least one member of the list including a computer, a finite state machine, a neural network and an inferential engine.

0017The invention includes at least one read method for the hard disk drive. Preferably, the read positioning method may be used after a read access of the read track fails. It often has a high probability of success, without the cost of iterative read access attempts based upon incrementing the read position of the read head. In some embodiments of the invention, after a read access using the read positioning method, the iterative read access attempts may be performed. These read methods may be used during initialization of the hard disk drive, and/or during normal operation of the hard disk drive.

0018The hard disk drive may include a servo controller driving a voice coil actuator to at least partly position the read head to read the read track on the rotating disk surface. The hard disk drive may further include the servo controller driving a micro-actuator to at least partly position the read head to read the read track on the rotating disk surface.

0019The hard disk drive may preferably include a computer directing the servo controller. The computer may be accessibly coupled with a memory containing program steps of a program system. The program system may direct the computer to implement the read positioning method and/or one of the invention's methods for reading the track. Preferably, at least one of the steps of the read positioning method may be at least partly implemented as a program step.

0020The step and/or means and/or program step determining the read PES burst pattern may include accessing a track location table to at least partly derive the read PES burst pattern for the read track position. The track location table may preferably reside in the memory accessibly coupled to the computer directing the servo controller.

0021The memory may include a non-volatile memory. A version of the program steps may be stored in the non-volatile memory. The version of the program steps preferably implements at least one of the following. An in-place-executable version of the program steps, a relocatable-version of the program steps, and a compression of the program steps.

0022The servo controller may preferably include a servo computer accessibly coupled with a servo memory. The invention's methods may be implemented in part by a servo program system directing the servo computer. The servo program system preferably includes servo program steps residing in the servo memory. The invention's methods may be implemented at least in part through the servo program steps.

0023The hard disk drive may include access of more than one rotating disk surface. The hard disk drive may further include access of rotating disk surfaces on more than one rotating disk. In certain embodiments, the track location table may reference a second rotating disk surface. In other alternative embodiments, the second rotating disk surface may be referenced by a second track location table.

BRIEF DESCRIPTION OF THE DRAWINGS

0024<figref idref="DRAWINGS">FIG. 1</figref> shows the invention's apparatus within the hard disk drive as the means for positioning at least one read head to access a read track on at least one rotating disk surface;

0025<figref idref="DRAWINGS">FIG. 2</figref> shows an alternative, often preferred, apparatus within the hard disk drive of <figref idref="DRAWINGS">FIG. 1</figref>, supporting the positioning method implemented by the program system which directs the computer, to at least partly position the read-write head using the voice coil motor and a micro-actuator;

0026<figref idref="DRAWINGS">FIG. 3</figref> shows a refinement of the hard disk drive of <figref idref="DRAWINGS">FIG. 2</figref>, supporting multiple read-write heads, each at least partly positioned by separate micro-actuators;

0027<figref idref="DRAWINGS">FIG. 4</figref> shows a schematic view of the hard disk drive of <figref idref="DRAWINGS">FIGS. 1 to 3</figref>, showing the read head within the read-write head accessing a track based at least partly upon the lever action of the voice coil motor;

0028<figref idref="DRAWINGS">FIG. 5</figref> shows a simplified diagram of the voice coil motor within the hard disk drive of <figref idref="DRAWINGS">FIGS. 1 to 4</figref>;

0029<figref idref="DRAWINGS">FIG. 6A</figref> shows a detail of the program system of <figref idref="DRAWINGS">FIG. 2</figref> for the method of read positioning and using that method of read positioning;

0030<figref idref="DRAWINGS">FIG. 6B</figref> shows a detail of <figref idref="DRAWINGS">FIG. 6A</figref> further supporting tentative reading of the read track, followed by use of the read positioning method when needed;

0031<figref idref="DRAWINGS">FIG. 7A</figref> shows a detail flowchart of <figref idref="DRAWINGS">FIG. 6B</figref> further reading the read track using the read positioning method, whenever the initial read access is not successful;

0032<figref idref="DRAWINGS">FIG. 7B</figref> shows a detail of <figref idref="DRAWINGS">FIG. 6A</figref> further tentatively reading the read track with the use of the read positioning method, before iterative reading with incremental positioning;

0033<figref idref="DRAWINGS">FIG. 8</figref> shows a detail of the read positioning method of <figref idref="DRAWINGS">FIG. 6A</figref>;

0034<figref idref="DRAWINGS">FIG. 9A</figref> shows a detail of <figref idref="DRAWINGS">FIG. 8</figref> further determining the read PES burst pattern;

0035<figref idref="DRAWINGS">FIG. 9B</figref> shows the rotating disk surface including the track, which includes multiple sectors;

0036<figref idref="DRAWINGS">FIG. 10A</figref> shows a format-oriented view of the track of <figref idref="DRAWINGS">FIGS. 4 and 9B</figref> including multiple sectors;

0037<figref idref="DRAWINGS">FIG. 10B</figref> shows the format-oriented view of the generic sector of <figref idref="DRAWINGS">FIG. 10A</figref>;

0038<figref idref="DRAWINGS">FIG. 10C</figref> shows the servo pattern of <figref idref="DRAWINGS">FIG. 10B</figref>;

0039<figref idref="DRAWINGS">FIG. 10D</figref> shows a detail of the PES burst pattern of <figref idref="DRAWINGS">FIG. 10C</figref>;

0040<figref idref="DRAWINGS">FIG. 10E</figref> shows the relationship between the PES burst pattern of <figref idref="DRAWINGS">FIG. 10C</figref> in three successive tracks on the same rotating disk surface;

0041<figref idref="DRAWINGS">FIG. 11A</figref> shows an example structure of the track location table of <figref idref="DRAWINGS">FIGS. 1 to 3</figref>;

0042<figref idref="DRAWINGS">FIG. 11B</figref> shows some details of the generic track location entry of <figref idref="DRAWINGS">FIG. 11A</figref>;

0043<figref idref="DRAWINGS">FIG. 11C</figref> shows an example of the relationship between derived signals based upon the demodulated PES burst pattern of successive tracks in the hard disk drive of the preceding Figures;

0044<figref idref="DRAWINGS">FIG. 12</figref> shows a schematic top view of the read head and the write head located above tracks of the rotating disk surface when reading and writing a logical track;

0045<figref idref="DRAWINGS">FIG. 13</figref> shows a schematic top view of a second read-write head, which includes a second read head and a second write head located above tracks of a second rotating disk surface when reading and writing the logical track;

0046<figref idref="DRAWINGS">FIG. 14</figref> shows a detail of the read positioning method of <figref idref="DRAWINGS">FIG. 6A</figref> for the second read-write head accessing the second rotating disk surface of <figref idref="DRAWINGS">FIG. 13</figref>;

0047<figref idref="DRAWINGS">FIG. 15A</figref> shows a method of making the hard disk drive, of the preceding Figures;

0048<figref idref="DRAWINGS">FIG. 15B</figref> shows the version list for the version of the program system to reside in the non-volatile memory of <figref idref="DRAWINGS">FIG. 3</figref>; and

0049<figref idref="DRAWINGS">FIG. 15C</figref> shows the track table version list for the version of the track location table to reside in the non-volatile memory of <figref idref="DRAWINGS">FIG. 3</figref>.

DETAILED DESCRIPTION

0050The invention includes a read positioning method and apparatus supporting the read positioning method in a hard disk drive. The method read positions at least one read head accessing a track on at least one rotating disk surface in a hard disk drive. It provides a quick and efficient way to adjust the read position of the read head based upon the Burst Correction Value of the nearest write track, when the PES burst patterns of the read track and nearest write track match.

0051<figref idref="DRAWINGS">FIG. 1</figref> shows an apparatus within the hard disk drive <b>10</b> supporting the positioning method of the invention by the means for positioning <b>3000</b> of at least one read head <b>500</b>R. The read head <b>500</b>R reads a read track <b>18</b> (shown in <figref idref="DRAWINGS">FIG. 4</figref>) on at least one rotating disk surface <b>12</b> in the hard disk drive <b>10</b>. The read head <b>50</b>OR is included in a read-write head <b>500</b>. The read-write head <b>500</b> typically includes a separate write head <b>500</b>W. The read-write head <b>500</b> is typically known as a merged read-write head, or as a merged, magnetoresistive read-write head, or further, as a merged, Giant MagnetoResistive (GMR) read-write head.

0052<figref idref="DRAWINGS">FIG. 2</figref> shows an alternative, often preferred, apparatus within the hard disk drive <b>10</b> of <figref idref="DRAWINGS">FIG. 1</figref>, supporting the positioning method implemented by the program system <b>1200</b> directing the computer <b>1100</b>, to at least partly position the read head <b>50</b>OR using a micro-actuator <b>310</b>.

0053<figref idref="DRAWINGS">FIG. 3</figref> shows a refinement of the hard disk drive <b>10</b> of <figref idref="DRAWINGS">FIG. 2</figref>, supporting multiple read-write heads, each at least partly positioned by separate micro-actuators.

0054<figref idref="DRAWINGS">FIG. 4</figref> shows a schematic view of the hard disk drive <b>10</b> of <figref idref="DRAWINGS">FIGS. 1 to 3</figref>, with the read head <b>500</b>R within the read-write head <b>500</b>, accessing a track <b>18</b> as the read track <b>3110</b> based at least partly upon the lever action of the voice coil motor <b>30</b>. The track <b>18</b> is located on the rotating disk surface <b>12</b>.

0055<figref idref="DRAWINGS">FIG. 5</figref> shows a simplified diagram of the voice coil motor <b>30</b> within the hard disk drive <b>10</b> of <figref idref="DRAWINGS">FIGS. 1 to 4</figref>.

0056The voice coil motor <b>30</b> of <figref idref="DRAWINGS">FIGS. 1 to 5</figref> includes the following. The voice coil <b>32</b> is mechanically coupled with at least one actuator arm <b>50</b>. The head gimbal assembly <b>60</b> is coupled with the actuator arm <b>50</b>. The head gimbal assembly <b>60</b> is coupled with the slider <b>90</b>, which contains the read-write head <b>500</b>. The voice coil <b>32</b> and actuator arm <b>50</b> are mounted on an actuator pivot <b>40</b>. The fixed magnet <b>20</b> is assembled about the voice coil <b>32</b>.

0057The operation of the voice coil motor <b>30</b> of <figref idref="DRAWINGS">FIGS. 1 to 5</figref> includes the following. A lever action occurs by applying a time-varying electrical signal <b>242</b> to the voice coil <b>32</b>. The time-varying electrical signal <b>242</b> causes the voice coil <b>32</b> to magnetically interact with the fixed magnet <b>20</b>, inducing movement of the coupled actuator arm <b>50</b> in the plane of the rotating disk surface <b>12</b>. The motion of the actuator arm <b>50</b> through the head gimbal assembly <b>60</b>, and the slider <b>90</b>, moves the read-write head <b>500</b>, which in turn positions the read head <b>500</b>R and the write head <b>500</b>W. Today, it is typical that the read head <b>500</b>R and the write head <b>500</b>W are concurrently positioned over distinct tracks on the rotating disk surface <b>12</b>. These concurrent track positions may be more than one, and often over twenty, tracks apart.

0058Some of the following figures show flowcharts of at least one method of the invention, possessing arrows with reference numbers. These arrows will signify flow of control and sometimes data supporting implementations including at least one program operation or program thread executing upon a computer, inferential links in an inferential engine, state transitions in a finite state machine, and dominant learned responses within a neural network.

0059The operation of starting a flowchart refers to at least one of the following. Entering a subroutine in a macro instruction sequence in a computer. Entering into a deeper node of an inferential graph. Directing a state transition in a finite state machine, possibly while pushing a return state. And triggering a collection of neurons in a neural network.

0060The operation of termination in a flowchart refers to at least one or more of the following. The completion of those operations, which may result in a subroutine return, traversal of a higher node in an inferential graph, popping of a previously stored state in a finite state machine, return to dormancy of the firing neurons of the neural network.

0061A computer as used herein will include, but is not limited to, an instruction processor. The instruction processor includes at least one instruction processing element and at least one data processing element. Each data processing element is controlled by at least one instruction processing element.

0062<figref idref="DRAWINGS">FIG. 6A</figref> shows a detail flowchart of the program system <b>1200</b> of <figref idref="DRAWINGS">FIG. 2</figref> for the method of read positioning, and using the read positioning method, for the read head <b>500</b>R. Operation <b>1212</b> supports the read positioning method for at least one read head <b>500</b>R accessing a read track <b>3110</b> on at least one rotating disk surface <b>12</b> in the hard disk drive <b>10</b>. Operation <b>1222</b> supports tentative reading of the read track <b>3110</b>, followed by use of the read positioning method <b>1212</b> when needed. Operation <b>1232</b> supports tentative reading of the read track <b>3110</b> with use of the read positioning method <b>1212</b> before iterative reading with incremental positioning.

0063<figref idref="DRAWINGS">FIG. 6B</figref> shows a detail flowchart of operation <b>1222</b> of <figref idref="DRAWINGS">FIG. 6A</figref> further supporting tentative reading of the read track, followed by use of the read positioning method when needed. Operation <b>1252</b> supports reading the read track <b>3110</b> with the read head <b>500</b>R to determine if an initial read access is successful. Operation <b>1262</b> supports reading the read track <b>3110</b> with the read head <b>500</b>R using the read positioning method <b>1212</b>, whenever the initial read access is not successful.

0064<figref idref="DRAWINGS">FIG. 7A</figref> shows a detail flowchart of operation <b>1262</b> of <figref idref="DRAWINGS">FIG. 6B</figref> further reading the read track <b>3110</b> with the read head <b>500</b>R using the read positioning method <b>1212</b>, whenever the initial read access is not successful. Operation <b>1282</b> determines whenever the initial read access is not successful. When the determination <b>1284</b> is Yes, operation <b>1286</b> supports reading the read track <b>3110</b> with the read head <b>500</b>R using the read positioning method <b>1212</b>. When the determination is No, the read position method <b>1212</b> is skipped.

0065<figref idref="DRAWINGS">FIG. 7B</figref> shows a detail flowchart of operation <b>1232</b> of <figref idref="DRAWINGS">FIG. 6A</figref> further tentatively reading the read track <b>3110</b>, with the use of the read positioning method <b>1212</b>, before iterative reading with incremental positioning. Operation <b>1312</b> supports reading the read track <b>3110</b> with the read head <b>500</b>R to determine if an initial read access is successful. Operation <b>1322</b> supports reading the read track <b>3110</b> with the read head <b>500</b>R using the read positioning method <b>1212</b> to determine if a second read access is successful, whenever the initial read access is not successful. Operation <b>1332</b> supports iteratively reading the read track with incremental positioning, whenever the second read access is not successful.

0066<figref idref="DRAWINGS">FIG. 8</figref> shows a detail flowchart for the read positioning method <b>1212</b> of <figref idref="DRAWINGS">FIG. 6A</figref>. Operation <b>1352</b> supports determining the read PES burst pattern <b>3100</b> of the read track <b>3110</b>. Operation <b>1362</b> supports using the read track position <b>3120</b> of the read track <b>3110</b> to find a nearest write track position <b>3130</b> for a write track <b>3140</b>. Operation <b>1372</b> supports predicting the write PES burst pattern <b>3150</b> of the write track <b>3140</b>. Operation <b>1382</b> supports adjusting the read position <b>3160</b> of the read head <b>500</b>R by the Burst Correction Value <b>3170</b> (BCV) of the write track <b>3140</b> whenever the write PES burst pattern <b>3150</b> matches the read PES burst pattern <b>3100</b>.

0067<figref idref="DRAWINGS">FIG. 9A</figref> shows a detail flowchart of operation <b>1352</b> of <figref idref="DRAWINGS">FIG. 8</figref> further determining the read PES burst pattern <b>3100</b> of the read track <b>3110</b>. Operation <b>1402</b> supports accessing the track location table <b>1150</b> to at least partly derive the read PES burst pattern <b>3100</b> for the read track position <b>3120</b>. Operation <b>1412</b> supports read-accessing a first sector in the read track <b>3110</b> to at least partly derive the read PES burst pattern <b>3100</b>. Operation <b>1422</b> supports read-accessing a second sector in the read track <b>3110</b> to at least partly further derive the read PES burst pattern <b>3100</b>. Operation <b>1432</b> supports predicting the read PES burst pattern <b>3100</b> based upon at least the read track position <b>3120</b>.

0068In <figref idref="DRAWINGS">FIG. 9A</figref>, operation <b>1402</b> is typically used in the normal operation of the hard disk drive <b>10</b>. The operations <b>1412</b>, <b>1422</b>, and <b>1432</b> are more commonly used during initialization of the hard disk drive <b>10</b>.

0069<figref idref="DRAWINGS">FIG. 9B</figref> shows the rotating disk surface <b>12</b> including the track <b>18</b>. The track <b>18</b> includes N sectors, where N is at least two. The track <b>18</b> includes multiple sectors, a first sector <b>22</b>-<b>1</b> and a second sector <b>22</b>-<b>2</b>, etc. until a last sector <b>22</b>-N. These sectors are successively read or written for the entire track <b>18</b> most if not all of the time. The hard disk drive <b>10</b> is shown moving the rotating disk surface <b>12</b> in a clockwise direction. One skilled in the art will recognize that it is equally feasible to move the rotating disk surface <b>12</b> in a counter clockwise direction. The invention is equally applicable and useful to hard disk drive irrespective of whether they rotate disk surfaces in a clockwise or counterclockwise direction. While the Figures and discussion of the application will focus on a clockwise movement of the rotating disk surface, this is being done to simplify the presentation, and is not meant to limit the scope of the claims or the invention.

0070<figref idref="DRAWINGS">FIG. 10A</figref> shows a format-oriented view of the track <b>18</b> of <figref idref="DRAWINGS">FIGS. 4 and 9B</figref>. The track <b>18</b> includes the first sector <b>22</b>-<b>1</b>, and the second sector <b>22</b>-<b>2</b>, successively to the last sector <b>22</b>-N. The track <b>18</b> is shown including a generic sector <b>22</b>-K. The generic sector <b>22</b>-K typically can be any of the sectors of the track <b>18</b>. In certain embodiments of the invention, format variations may exist between some of the sectors.

0071<figref idref="DRAWINGS">FIG. 10B</figref> shows the format-oriented view of a generic sector <b>22</b>-K. The generic sector <b>22</b>-K includes servo pattern <b>24</b> and sector data <b>26</b>. The servo pattern <b>24</b> will be discussed in some detail through <figref idref="DRAWINGS">FIGS. 10C to 11D</figref>. The sector data <b>26</b> typically contains a logical data sector and at least an Error Detection Code, often an Error Correction/Detection Code. The local data sector and Error Code fields are read as bits and processed to derive an error corrected/detected indication and an error corrected logical data sector. When the error corrected/detected indication does not indicate uncorrectable errors in the logical data sector, the hard disk drive <b>10</b> will use the error corrected logical data sector as the accessed value of the data in the sector data <b>26</b>.

0072<figref idref="DRAWINGS">FIG. 10C</figref> shows the servo pattern <b>24</b> of <figref idref="DRAWINGS">FIG. 10B</figref> including an AGC field <b>70</b>, a Position Error Signal burst pattern, which will be referred herein the PES burst pattern <b>72</b>, a gray code <b>74</b>, at least one synchronization field <b>76</b>, and possibly a Burst Correction Value field <b>78</b>. The Automatic Gain Control, or AGC field <b>70</b> is used to calibrate the gain of the read preamplifier in the read-write preamplifier <b>522</b>, shown in <figref idref="DRAWINGS">FIGS. 1 to 3</figref>. The PES burst pattern <b>72</b> is used by the channel interface <b>1140</b> to generate the PES signal <b>272</b>, shown in <figref idref="DRAWINGS">FIGS. 1 to 3</figref>. The synchronization field <b>76</b> is used to synchronize the timing for receipt of the sector data <b>26</b>. In certain embodiments, there may be more than one of the synchronization fields.

0073In <figref idref="DRAWINGS">FIG. 10C</figref>, the gray code <b>74</b> is used to determine the track number, which the read head <b>500</b>R is targeting. The gray code also acts as the absolute identification of a specific track <b>18</b>. Each track on a rotating disk surface will have a distinct gray code. Gray codes have the characteristic that two successive gray code values differ in exactly one bit position from each other. The gray code of two successive track consequently differ in only one bit position.

0074<figref idref="DRAWINGS">FIG. 10D</figref> shows a detail of the PES burst pattern <b>72</b>, including at least an A signal <b>80</b> and a B signal <b>82</b>. Frequently, and often preferably, the PES burst pattern <b>72</b> also includes a C signal <b>84</b> and a D signal <b>86</b>. In some embodiments of the invention, the PES burst pattern <b>72</b> may further, preferably, include an E signal <b>87</b> and an F signal <b>88</b>. To simplify the discussion, the application will focus on the PES burst pattern <b>72</b> including the A signal <b>80</b>, the B signal <b>82</b>, the C signal <b>84</b> and the D signal <b>86</b>. This is being done strictly to simplify the discussion and is not meant to limit the scope of the invention and its claims.

0075<figref idref="DRAWINGS">FIG. 10E</figref> shows the relationship between the PES burst pattern <b>72</b> in three successive tracks on the same rotating disk surface <b>12</b> arranged in the radial direction <b>14</b> of <figref idref="DRAWINGS">FIG. 4</figref>. The first track <b>18</b>-J is written about a first track center path <b>16</b>-J. The second track <b>18</b>-J+1 is written about a second track center path <b>16</b>-J+1. The third track <b>18</b>-J+2 is written about a third track center path <b>16</b>-J+2.

0076In <figref idref="DRAWINGS">FIG. 10E</figref>, the A signal <b>80</b>, and the B signal <b>82</b> are typically written to the rotating disk surface as modulated analog patterns with respect to the center path of each track. The C signal <b>84</b> and the D signal <b>86</b> are typically written to the rotating disk surface as modulated analog patterns with respect to the midpoint between each pair of tracks. The PES burst pattern <b>72</b> typically repeats itself in each generic sector <b>22</b>-K within a track <b>18</b>. The PES burst pattern <b>72</b> typically repeats itself every two tracks in the radial direction <b>14</b> as shown in <figref idref="DRAWINGS">FIG. 4</figref>.

0077In <figref idref="DRAWINGS">FIG. 10E</figref>, the A signal <b>80</b> and the B signal <b>82</b> are typically written together on the rotating disk surface <b>12</b> centered about the center path of every track. The first A Signal <b>90</b>-<b>1</b> and the first B signal <b>92</b>-<b>1</b> are centered about the first track center path <b>16</b>-J of the first track <b>18</b>-J. The first B signal <b>92</b>-<b>1</b> and the second A signal <b>90</b>-<b>2</b> are centered about the second track center path <b>16</b>-J+1 of the second track <b>18</b>-J+1. The second A signal <b>90</b>-<b>2</b> and the second B signal <b>92</b>-<b>2</b> are centered about the third track center path <b>16</b>-J+2 of the third track <b>18</b>-J+2.

0078In <figref idref="DRAWINGS">FIG. 10E</figref>, the C signal <b>84</b> and the D signal <b>86</b> are typically written to the rotating disk surface as modulated analog patterns with respect to the midpoint between each pair of tracks. The first C signal <b>96</b>-<b>1</b> and the first D signal <b>98</b>-<b>1</b> are centered about the midpoint between the first track center path <b>16</b>-J and the second track center path <b>16</b>-J+1. The second C signal <b>96</b>-<b>2</b> and the first D signal <b>98</b>-<b>1</b> are centered about the midpoint between the second track center path <b>16</b>-J+1 and the third track center path <b>16</b>-J+2.

0079<figref idref="DRAWINGS">FIG. 11A</figref> shows an example structure of the track location table <b>1150</b> of <figref idref="DRAWINGS">FIGS. 1 to 3</figref>. Typically, there is a track location entry <b>1152</b> for each track <b>18</b> accessible by the hard disk drive <b>10</b>. The track location table <b>1150</b> includes a first track location entry <b>1152</b>-<b>1</b>, a second track location entry <b>1152</b>-<b>2</b> and a generic track location entry <b>1152</b>-K

0080<figref idref="DRAWINGS">FIG. 11B</figref> shows some details of the generic track location entry <b>1152</b>-K of <figref idref="DRAWINGS">FIG. 11A</figref>. Typically, and preferably, the track location table may include the following. A logical track number <b>1154</b>, which is used by the hard disk drive <b>10</b> as the external, logical reference to the track. A target read gray code <b>1156</b>, which is the gray code of the track to be read when the read head <b>500</b>R is to read the track <b>18</b> associated with the logical track number <b>1154</b>. The target read gray code may also include a track offset in terms of a fraction of the track width. A target write gray code <b>1158</b>, which is the gray code of the track to be read by the read head <b>500</b>R, when the write head <b>500</b>W is to write the track <b>18</b> associated with the logical track number <b>1154</b>.

0081Often, the hard disk drive <b>10</b> uses more than one rotating disk surface <b>12</b> for data storage. In such embodiments, the generic track location entry <b>1152</b>-K may preferably further include a rotating disk surface indicator <b>1159</b> as shown in <figref idref="DRAWINGS">FIG. 11B</figref>. Alternatively, a second track location table <b>1151</b>, similar to the track location table <b>1150</b>, may be used to account for the logical tracks of the second rotating disk surface, as shown in <figref idref="DRAWINGS">FIG. 3</figref>.

0082<figref idref="DRAWINGS">FIG. 11C</figref> shows an example of the relationship between derived signals based upon the demodulated PES burst pattern <b>72</b> of successive tracks in the hard disk drive <b>10</b>. The derived signal A−B is created from the demodulated amplitude of the A signal <b>80</b> subtracted from the demodulated amplitude of the B signal <b>82</b>. The derived signal C−D is created from the demodulated amplitude of the C signal <b>84</b> subtracted from the demodulated amplitude of the D signal <b>86</b>.

0083In <figref idref="DRAWINGS">FIG. 11C</figref>, the derived signal (A−B)+(C−D) is the clamped sum of the derived signal A−B and the derived signal C−D. The clamping of the sum will be assumed to be symmetric about zero, so that following is performed. If (A−B)+(C−D) is greater than or equal to the clamp value, then the derived signal (A−B)+(C−D) equals the clamp value. If (A−B)+(C−D) is greater than the negated clamp value and (A−B)+(C−D) is less than the clamp value, then the derived signal (A−B)+(C−D) equals the value of (A−B)+(C−D). If (A−B)+(C−D) is less than or equal to the negated clamp value and (A−B)+(C−D) is less than the clamp value, then the derived signal (A−B)+(C−D) equals the negated clamp value.

0084In <figref idref="DRAWINGS">FIG. 11C</figref>, the derived signal (A−B)−(C−D) is the clamped difference of the derived signal A−B and the derived signal C−D derived in a similar fashion to the derived signal (A−B)+(C−D).

0085To provide the greatest accuracy in deriving the PES signal <b>272</b>, the channel interface <b>1140</b> uses the derived signal which is closest to zero, given the distance of the read head <b>500</b>R from the center of the track <b>18</b>. The derived signal closest to zero is considered to provide the preferred estimator for the PES signal <b>272</b>, because it has the best linearity within the channel interface <b>1140</b>, in terms of the read head <b>500</b>R distance from the center of the track <b>18</b>.

0086In <figref idref="DRAWINGS">FIG. 11C</figref>, the following derived signals are closest to zero for the read head <b>500</b>R at different distances from a track center. The distance between a track center and a successive track center will be assumed to be at least 100%, often 125%. The distance of the read head <b>500</b>R from the track center is called the target location.

0087In <figref idref="DRAWINGS">FIG. 11C</figref>, if −50% is less than or equal to the target location, and the target location is less than −40%, Then the derived signal C−D is closest to zero. The derived signal C−D is used to estimate the PES signal <b>272</b>. If −40% is less than or equal to the target location, and the target location is less than −10%, Then the derived signal (A−B)−(C−D) is closest to zero. The derived signal (A−B)−(C−D) is used to estimate the PES signal <b>272</b>.

0088In <figref idref="DRAWINGS">FIG. 11C</figref>, if −10% is less than or equal to the target location, and the target location is less than −10%, Then the derived signal (A−B) is closest to zero. The derived signal (A−B) is used to estimate the PES signal <b>272</b>. If 10% is less than or equal to the target location, and the target location is less than 40%, Then the derived signal (A−B)+(C−D) is closest to zero. The derived signal (A−B)+(C−D) is used to estimate the PES signal <b>272</b>. If 40% is less than or equal to the target location, and the target location is less than 50%, Then the derived signal C−D is closest to zero. The derived signal C−D is used to estimate the PES signal <b>272</b>.

0089In <figref idref="DRAWINGS">FIG. 11C</figref>, an alternative mechanism can be used to select the derived signal closest to zero. If −50% is less than the target location, and the target location is less than or equal to −40%, Then the derived signal C−D is closest to zero. The derived signal C−D is used to estimate the PES signal <b>272</b>. If −40% is less than the target location, and the target location is less than or equal to −10%, Then the derived signal (A−B)−(C−D) is closest to zero. The derived signal (A−B)−(C−D) is used to estimate the PES signal <b>272</b>. If −10% is less than the target location, and the target location is less than or equal to −10%, Then the derived signal (A−B) is closest to zero. The derived signal (A−B) is used to estimate the PES signal <b>272</b>. If 10% is less than the target location, and the target location is less than or equal to 40%, Then the derived signal (A−B)+(C−D) is closest to zero. The derived signal (A−B)+(C−D) is used to estimate the PES signal <b>272</b>. If 40% is less than the target location, and the target location is less than or equal to 50%, Then the derived signal C−D is closest to zero. The derived signal C−D is used to estimate the PES signal <b>272</b>.

0090<figref idref="DRAWINGS">FIG. 12</figref> shows a schematic top view of the read head <b>500</b>R and the write head <b>500</b>W located above tracks of the rotating disk surface <b>12</b> when reading and writing a logical track. By way of example, consider accesses to logical track number <b>30</b> and logical track number <b>50</b> both located on the rotating disk surface <b>12</b>. The distance between the read head <b>500</b>R and the write head <b>500</b>W will be assumed to be <b>25</b> and one half of the gray code tracks. The data tracks will be assumed to be spaced every one and a quarter of the gray code tracks. The read head location for writing <b>500</b>-R<b>1</b> is the track location that the read head <b>500</b>R targets for the write head <b>500</b>W to write a track <b>18</b>, given the distance between the read head <b>500</b>R and the write head <b>500</b>W.

0091<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE ONE</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>An example of the track location table 1150 of</entry></row><row><entry>FIGS. 1 to 3, 9A, and 11A with each row representing</entry></row><row><entry>the generic track location entry 1152-K.</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="77pt" align="center" /><colspec colname="2" colwidth="56pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Logical track</entry><entry>Target write</entry><entry>Target read</entry></row><row><entry>number 1154</entry><entry>gray code 1158</entry><entry>gray code 1156</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="77pt" align="center" /><colspec colname="2" colwidth="56pt" align="char" char="." /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>29</entry><entry>73.5</entry><entry>99</entry></row><row><entry>30</entry><entry>74.75</entry><entry>100.25</entry></row><row><entry>31</entry><entry>76</entry><entry>101.5</entry></row><row><entry>. . .</entry><entry>. . .</entry><entry>. . .</entry></row><row><entry>49</entry><entry>98.5</entry><entry>124</entry></row><row><entry>50</entry><entry>99.75</entry><entry>125.25</entry></row><row><entry>51</entry><entry>101</entry><entry>126.5</entry></row><row><entry>. . .</entry><entry>. . .</entry><entry>. . .</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0092Each generic track location entry <b>1152</b>-K in Table One includes the following: The logical track number <b>1154</b> is in the first column entry on the left. The target write gray code <b>1158</b> is in the middle column. The target write gray code <b>1158</b> may also include a fractional part, indicating which of the derived signals for the PES burst pattern <b>72</b> will be closest to zero and offer the best estimator for the channel interface <b>1140</b> to use in generating the PES signal <b>272</b>. The target read gray code <b>1156</b> is in the third column from the left. Note that the target read gray code <b>1156</b> may include a fractional part, indicating which of the derived signals for the PES burst pattern <b>72</b> will be closest to zero and offer the best estimator for the channel interface <b>1140</b> to use in generating the PES signal <b>272</b>.

0093Consider writing the track <b>18</b> for the logical track number <b>1154</b> with value of 30, as shown in the second row from the top in the example Table One. For convenience, refer to this track as data track <b>30</b>. According to the example of the track location table <b>1150</b> found in Table One, the value of the target write gray code <b>1158</b> is 74.75. <figref idref="DRAWINGS">FIG. 12</figref> shows read head <b>500</b>R following at the read head location for writing <b>500</b>-R<b>1</b>, which is positioned 25% above the gray code track <b>74</b>, referenced as <b>18</b>–<b>74</b>. This is the track location with the target write gray code <b>1158</b> value, of 74.75.

0094Consider writing the track <b>18</b> associated with the logical track number <b>1154</b> having the value of 50, as found in the second row from the bottom in the example Table One. For convenience, refer to this track as data track <b>50</b>. According to the example of the track location table <b>1150</b> found in Table One, the value of the target write gray code <b>1158</b> is 99.75. <figref idref="DRAWINGS">FIG. 12</figref> shows read head <b>500</b>R following at the second read head location for writing <b>500</b>-R<b>2</b>, which is repositioned 25% above the gray code track <b>100</b>, referenced as <b>18</b>–<b>100</b>. This is the track location associated with the target write gray code <b>1158</b> value of 99.75.

0095Now consider what happens if a read attempt fails for either of the two read methods portrayed as operations <b>1222</b> or <b>1232</b> in <figref idref="DRAWINGS">FIGS. 6A to 7B</figref>. Suppose the read head <b>500</b>R is attempting to read data track <b>30</b> and fails, leading to using the read positioning method. The read positioning method is described in <figref idref="DRAWINGS">FIGS. 8 and 9A</figref>.

0096In <figref idref="DRAWINGS">FIG. 8</figref>, operation <b>1352</b> determines the read PES burst pattern <b>3100</b> for the read track <b>3110</b> value of 30. <figref idref="DRAWINGS">FIG. 9A</figref> includes operation <b>1402</b>, which accesses the track location table <b>1150</b> as shown in the example Table One. The second row, third column from the left indicates a target read gray code <b>1156</b> value of 100.25, which is the determined read track position <b>3120</b>. The fractional part is 0.25 or 25% indicating the AB PES burst pattern can be used.

0097In <figref idref="DRAWINGS">FIG. 8</figref>, operation <b>1362</b> uses the read track position <b>3120</b> to determine the nearest write track position <b>3130</b> for the write track <b>3140</b>. Examining Table One, we find the nearest write track position in Column 2 is 99.75, for data track <b>50</b>, which is the value of the write track <b>3140</b>.

0098In <figref idref="DRAWINGS">FIG. 8</figref>, operation <b>1372</b> predicts the write PES burst pattern <b>3150</b> of the write track <b>3140</b>. Again referring to Table One, the fractional part of the nearest write track position value is 100–0.25, or 25% indicating the same PES burst pattern can be used, based upon <figref idref="DRAWINGS">FIG. 10E</figref>.

0099In <figref idref="DRAWINGS">FIG. 8</figref>, operation <b>1382</b> uses the Burst Correction Value <b>3170</b> of the write track to offset position of the read head <b>500</b>R, since the same PES burst patterns can be used.

0100<figref idref="DRAWINGS">FIG. 13</figref> shows a schematic top view of a second read-write head <b>502</b>, which includes a second read head <b>502</b>R and a second write head <b>502</b>W located above tracks of a second rotating disk surface <b>12</b>-<b>2</b> when reading and writing a logical track. By way of example, consider accesses to logical track number <b>130</b> and logical track number <b>150</b> both located on the second rotating disk surface <b>12</b>-<b>2</b>. The distance between the second read head <b>502</b>R and the second write head <b>502</b>W will be assumed to be 25 and one half of the gray code tracks. The data tracks will be assumed to be spaced every one and a quarter of the gray code tracks. The second read head location for writing <b>502</b>-R<b>1</b> is the track location the second read head <b>502</b>R targets for the second write head <b>502</b>W to write a track <b>18</b> when traveling over the second rotating disk surface <b>12</b>-<b>2</b>.

0101The second rotating disk surface <b>12</b>-<b>2</b> of <figref idref="DRAWINGS">FIG. 13</figref> and the rotating disk surface <b>12</b> of the preceding Figures may belong to the same rotating disk. Alternatively, they may belong to distinct rotating disks included in the hard disk drive <b>10</b>. The method and apparatus of the invention applies to embodiments with more than two rotating disk surfaces. The method and apparatus of the invention applies to embodiments with more than one rotating disk.

0102Apparatus supporting the read positioning method <b>1212</b> may include a means for at least partly performing each step or operation of the read positioning method shown in <figref idref="DRAWINGS">FIGS. 6A to 8</figref> and <b>14</b>. The means may include the following as shown in <figref idref="DRAWINGS">FIG. 1</figref>. Means for determining <b>3002</b> the read PES burst pattern <b>3100</b> of the read track <b>3110</b>. Means for using <b>3004</b> the read track position <b>3120</b> of the read track <b>3110</b> to find a nearest write track position <b>3130</b> for a write track <b>3140</b>. Means for predicting <b>3006</b> the write PES burst pattern <b>3150</b> of the write track <b>3140</b>. And means for adjusting <b>3008</b> the read position <b>3160</b> of the read head <b>500</b>R by the Burst Correction Value <b>3170</b> of the write track <b>3140</b> whenever the write PES burst pattern <b>3150</b> matches the read PES burst pattern <b>3100</b>. Further, the means for positioning <b>3000</b> may entirely provide the apparatus supporting the read positioning method <b>1212</b> of <figref idref="DRAWINGS">FIGS. 6A to 8</figref>, and <b>14</b>.

0103At least one of the means <b>3000</b> to <b>3008</b> may include at least one instance of at least one member of the list including: a computer, a finite state machine, a neural network and an inferential engine. A computer, as used herein, includes at least one instruction processor. An instruction processor includes at least one instruction processing element and at least one data processing element. Each of the data processing elements is controlled by at least one of the instruction processing elements. Preferably, the means for positioning <b>3000</b> may be embodied within the program system <b>1200</b> of <figref idref="DRAWINGS">FIG. 2 and 3</figref>. Alternatively, the means for positioning may be embodied within the servo program system <b>2000</b> of <figref idref="DRAWINGS">FIGS. 1 and 2</figref>. While the invention includes both implementations, the discussion of the means for positioning <b>3000</b> will be discussed in terms of the program system <b>1200</b>. This has been done to simplify the discussion and is not meant to limit the scope of the claims.

0104In <figref idref="DRAWINGS">FIGS. 1 to 3</figref>, the servo controller <b>1030</b> drives the voice coil <b>32</b> to at least partly position the read head <b>500</b>R to read access the read track <b>3110</b> on the rotating disk surface <b>12</b>. The hard disk drive <b>10</b> of <figref idref="DRAWINGS">FIGS. 2 and 3</figref> further include the servo controller <b>1030</b> driving a micro-actuator <b>310</b> to at least partly read position the read head <b>500</b>R to read access the read track <b>3110</b> on the rotating disk surface <b>12</b>.

0105The steps of the read positioning method <b>1212</b> of <figref idref="DRAWINGS">FIG. 6A</figref> are described in terms of the operations of <figref idref="DRAWINGS">FIGS. 8</figref>, <b>9</b>A, and <b>14</b>, as well as in terms of the track location table <b>1150</b> in <figref idref="DRAWINGS">FIGS. 2</figref>, <b>3</b>, <b>11</b>A, <b>11</b>B and Table One. The use of the read positioning method <b>1212</b> is described in <figref idref="DRAWINGS">FIGS. 6A to 7B</figref>.

0106The hard disk drive may preferably include a computer <b>1100</b> directing the servo controller <b>1030</b> as in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>. The computer <b>1100</b> may be accessibly coupled <b>1122</b> with a memory <b>1120</b> containing program steps of a program system <b>1200</b>. The program system <b>1200</b> may direct the computer to implement the read positioning method <b>1212</b> and/or one of the read methods <b>1222</b> and/or <b>1232</b>. Preferably, at least one of the steps of the read positioning method <b>1212</b> may be at least partly implemented as a program step. The program steps may implement the operations of the flowcharts.

0107The step and/or program step <b>1352</b> of <figref idref="DRAWINGS">FIG. 8</figref> and/or means for determining <b>3002</b> of <figref idref="DRAWINGS">FIG. 1</figref>, the read PES burst pattern <b>3100</b> may include the following. Accessing a track location table <b>1150</b> to at least partly derive the read PES burst pattern <b>3100</b> for the read track position <b>3120</b>. The track location table <b>1150</b> is shown in <figref idref="DRAWINGS">FIGS. 1 to 3</figref>, <b>11</b>A, <b>11</b>B, and Table One. The track location table <b>1150</b> may preferably reside in the memory <b>1120</b> accessibly coupled <b>1122</b> to the computer <b>1100</b> directing the servo controller.

0108The invention includes at least one read method for the hard disk drive. Preferably, the read positioning method <b>1212</b> of <figref idref="DRAWINGS">FIG. 6A</figref> may be used after a read access of the read track fails as outlined in <figref idref="DRAWINGS">FIGS. 6B and 7A</figref>. It often has a high probability of success, without the cost of iterative read access attempts based upon incrementing the read position of the read head. In some embodiments of the invention, after a read access using the read positioning method <b>1212</b>, the iterative read access attempts may be performed as in <figref idref="DRAWINGS">FIG. 7B</figref>. These read methods may be used during initialization of the hard disk drive <b>10</b>, and/or during normal operation of the hard disk drive. When used during the initialization, it is often unnecessary for the program system to reside in a non-volatile memory. When used during normal operation, it is often preferred for the program system <b>1200</b> to reside in a non-volatile memory <b>1126</b>.

0109In <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the servo controller <b>1030</b> may preferably include a servo computer <b>1050</b> second accessibly coupled <b>1032</b> with a servo memory <b>1040</b>. The invention's methods may be implemented in part by a servo program system <b>2000</b> directing the servo computer <b>1050</b>. The servo program system <b>2000</b> preferably includes servo program steps residing in the servo memory <b>1040</b>.

0110The hard disk drive <b>10</b> may include more than one accessible rotating disk surface as shown in <figref idref="DRAWINGS">FIGS. 12 and 13</figref>. In certain embodiments, the track location table <b>1150</b> may reference a second rotating disk surface <b>12</b>-<b>2</b>, as indicated by the use of a rotating disk surface indicator <b>1159</b> in <figref idref="DRAWINGS">FIG. 11B</figref>. In other alternative embodiments, the second rotating disk surface <b>12</b>-<b>2</b> may be referenced by a second track location table <b>1151</b> as in <figref idref="DRAWINGS">FIG. 3</figref>.

0111<figref idref="DRAWINGS">FIG. 14</figref> shows a detail flowchart of the read positioning method <b>1212</b> of <figref idref="DRAWINGS">FIG. 6A</figref> for the second read-write head <b>502</b> accessing the second rotating disk surface <b>12</b>-<b>2</b> of <figref idref="DRAWINGS">FIG. 13</figref>. Operation <b>1452</b> supports determining the second read PES burst pattern <b>3100</b> of the second read track <b>3110</b>. Operation <b>1462</b> supports using the second read track position <b>3120</b> of the second read track <b>3110</b> to find a second nearest write track position <b>3130</b> for a second write track <b>3140</b>. Operation <b>1472</b> supports determining the second write PES burst pattern <b>3150</b> of the second write track <b>3140</b>. Operation <b>1482</b> supports using the Burst Correction Value <b>3170</b> of the second write track <b>3140</b> to adjust the read position <b>3160</b> of the second read head <b>502</b>R whenever the second write PES burst pattern <b>3150</b> matches the second read PES burst pattern <b>3100</b>.

0112In <figref idref="DRAWINGS">FIG. 14</figref>, by way of example, the second read PES burst pattern may be distinct from the read PES burst pattern <b>3100</b>, however it is usually preferred that they be essentially the same. The discussion of <figref idref="DRAWINGS">FIG. 14</figref> is done in that fashion to simplify that discussion and not to limit the scope of the claims.

0113The memory <b>1120</b> may include a non-volatile memory <b>1126</b> as in <figref idref="DRAWINGS">FIG. 3</figref>. A version of the program steps of the program system <b>1200</b> may reside in the non-volatile memory. The servo memory <b>1040</b> of <figref idref="DRAWINGS">FIGS. 1 and 2</figref> may include a servo non-volatile memory similar to the non-volatile memory <b>1126</b> in <figref idref="DRAWINGS">FIG. 3</figref>. A version of the program steps of the servo program system <b>2000</b> may be stored in the servo non-volatile memory in a similar fashion.

0114The invention includes a method of making <b>2900</b> the hard disk drive <b>10</b>, as shown in <figref idref="DRAWINGS">FIG. 15A</figref>. The method may include either and/or both of the operations. Operation <b>2912</b> supports programming the non-volatile memory <b>1126</b> within the memory <b>1120</b> to include a version of the program steps of the program system <b>1200</b>. The version of the program steps implements at least one member of the version list <b>3100</b> shown in <figref idref="DRAWINGS">FIG. 15B</figref>. Operation <b>2922</b> support programming the non-volatile memory <b>1126</b> to include a version of the track location table <b>1150</b>. The version of the track location table <b>1150</b> implements at least one member of the track table version list <b>3200</b> shown in <figref idref="DRAWINGS">FIG. 15C</figref>. The invention includes the hard disk drive <b>10</b>, as a product of the process of the method of making <b>2900</b>, shown in <figref idref="DRAWINGS">FIG. 15A</figref>. The track location table <b>1150</b> generated using the read methods of this invention is also the product of the invention's process.

0115<figref idref="DRAWINGS">FIG. 15B</figref> shows the version list <b>3100</b> including: an in-place-executable version of the program steps <b>3102</b>, a relocatable-version of the program steps <b>3104</b>, and a compression of the program steps <b>3106</b>. <figref idref="DRAWINGS">FIG. 15C</figref> shows the track table version list <b>3200</b> including: a relocatable-version of the track location table <b>3202</b>, and a compression of the track location table <b>3204</b>.

0116Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.